Execution of a BACKSPACE statement causes the disc file connected to the
specified unit to be positioned before the preceding record. If there is no
preceding record, the position of the file is unchanged. If the preceding
record is an endfile record, the file is positioned before the endfile
You cannot backspace over a record that has been written using
The following specifiers are associated with the BACKSPACE statement:
<value> specifies the unit number. The keyword and equals sign are
optional if this is the first item in the list. If unit number is the only
argument, the brackets around the argument list are optional.
<variable> will contain zero if the operation was successful, otherwise a
positive value to indicate an error.
<label> specifies a label to go to in the event of an error.